A conventional surgical scalpel comprises a reusable handle having a tang at one end on which a replaceable slotted blade is mounted. The handle is intended to be used repeatedly, but the blade is normally discarded after each instance of use. Some operations may require several blades to be used successively on the same handle, e.g. where the blades become dull or contaminated, or a different style of blade is required at different stages of the operation.
To remove the blade from the handle, the heel portion of the slotted blade shown in FIG. 1 must be bent out of its plane (i.e. transversely to the handle), and then moved axially along the tang so that the heel portion rides over the tang thereby releasing the tang from the slot. The slot is of keyhole shape, which as seen in the figure is wider at the rear than at the front so as to facilitate partial insertion of the tang into the wide front portion of the slot. The tang has a recessed protrusion dimensioned for securing the narrow sides of the slot. The length of keyhole slot is the same as the protrusion, so that when the blade is mounted on the protrusion and pushed backward, the narrow portion of the keyhole slot engages opposing recesses in the sides of the protrusion toward its front edge. The blade is then secured by sliding along the protrusion until a rear edge of the wide portion of the keyhole slot engages a rear edge of the protrusion. Manual removal of the blade requires that the rear edge of the keyhole slot be raised clear of the rear edge of the protrusion so as to allow the blade to be slid along the recesses in a reverse procedure. This can be difficult, particularly when the scalpel is wet. With the ever increasing spread of blood transmitted diseases, the removal is also a dangerous procedure as any accidental injury from the blade can have life-threatening ramifications.
Many devices have been developed in an effort to facilitate the removal of the blade from the scalpel, and to render the removal procedure less dangerous. Some require two-handed operation such as those described in GB 1 596 199, U.S. Pat. Nos. 244,094, 4,378,624, 730,376, 4,903,390, 5,088,173 and 5,163,553. Other devices require the user to bend, pivot or flex the scalpel handle to cause the blade to be dismounted such as those described in U.S. Pat. Nos. 1,648,408, 4,168,777, 4,270,416, 4,466,539, 4,736,844, 4,746,016 and 5,035,703.
U.S. Pat. No. 5,875,533 discloses a device for removing a blade from the tang of a scalpel. The scalpel is inserted in, and withdrawn from, the blade remover, which has a rocker block that pivots about an axis transverse to the insertion path. When the scalpel is inserted into the blade remover, its tang pushes against a contact surface of the rocker block, causing the rocker block to pivot. Legs at the other end of the rocker block apply a transverse force to the heel of the blade on either side of the tang, thereby lifting the heel of the blade off the tang and allowing its removal. The blade remover may be mounted in the lid of a sharps container.
What appears to characterize known devices is that a specialized removal tool is provided into which the scalpel is inserted. Upon insertion, the blade is retained within the tool allowing the tang to be removed. Tools that allow single-handed operation appear generally to be bulky and often to require anchoring in some way.
In order to allow conventional blade removal devices to make contact with the blade in order to provide the required purchase that allows such devices to operate it is usual for the blade to be wider than the tang. The resulting overhang on either side of the tang allows the blade to be gripped by the blade removal device, this of course being a prerequisite to its effective removal. However, it has been found that this is prone to a number of disadvantages. First, in use the blade is not supported by the tang over its entire surface and the narrower the tang the more pronounced this is, leading to unstable support of the blade.
Secondly, and independent of its width, in most known scalpels, the tang has a flat support surface for supporting parallel tracks that accommodate the narrow portion of keyhole slot in the blade. The tracks necessarily are slightly narrower than the width of the narrow portion of the keyhole slot, thus giving rise to a certain play which manifests itself as wobble. This is undesirable and militates against precise control of the blade, which is clearly a prerequisite for fine surgical procedures.
One exception to this construction of which we are aware is U.S. Design Pat. No. D 589,619 to Wu, which discloses a shaped disposable scalpel. The scalpel has a flat tang whose width is the same as the blade.
The blade is held flat against the tang apart from the rear edge of the blade, which is slightly lifted by the stepped portion of the tang and abuts a shaped recess in the handle. The stepped portion of the tang creates an air gap between the lower surface of the blade and the tang. This allows insertion of a thin flat object, which can then lift the rear portion of the blade off the tracked protrusion and allow the blade to be slid off the tracked protrusion in known manner. This appears to be the only way to remove the blade since there is no purchase at its rear edge owing to its abutting proximity with the shaped recess of the handle. Likewise, as noted above, there is no purchase at the sides of the blade owing to its width being the same as the tang.
U.S. Pat. No. 2,257,141 discloses a surgical knife comprising a handle having at one end a mount having a projection that supports a slot in a scalpel blade. The handle has an elongated groove that passes under the heel of the blade, thus facilitating its removal from the handle. Removal of the blade requires two simultaneous actions. First, the rear edge of the blade is grasped using forceps inserted into the groove. The blade is then flexed so that its heel is lifted from the projection and the blade is the grasped at its forward end and pulled off the mount.
U.S. Pat. Nos. 1,448,305 and 2,454,353 disclose arrangements for connecting and securing together a removable scalpel blade and a handle. The handle has a tang having a pin that engages an aperture in the blade, which is flexed so that a rear edge of the blade is frictionally supported by a rear landing of the handle.
U.S. Pat. No. 4,903,390 discloses a scalpel blade removal and storage apparatus having a disposable plastic housing having an internal channel for receiving the blade and positively locates the tang portion of the handle within the housing. The blade stripping mechanism comprises an integrally formed, spring loaded lever arm disposed externally of the housing. Pressing the lever deflects the heel of the blade away from the tang and over into a recessed stop or pocket formed near the forward portion of the housing. Retraction of the handle strips the blade from the handle.
GB 1 596 199 discloses an apparatus for removing the blade from a scalpel handle wherein the blade is mounted on the scalpel handle via a grooved boss with a shoulder engaging a slot in the blade. The apparatus includes a body having an aperture to receive the blade end of the scalpel and abutment means adjacent the aperture to deform the blade to disengage it from the shoulder and hold the blade while the handle is withdrawn.
WO 2010/000989 discloses a blade removal device having two articulated jaws that are commonly hinged at their ends and whose opposite ends have scissor-type handles allowing the jaws to be operated between thumb and forefinger. A blade is inserted into the space between the jaws, which are then closed so as to grip the blade and allow its removal from its handle by a lateral pulling movement.
GB 2 417 453 discloses a blade removal device for a scalpel having two hingedly connected components defining opposing shaped recesses for accommodating a scalpel blade, which retained inside the device when the scalpel handle is withdrawn.
There is clearly a need for a scalpel whose handle may be non-disposable but to which disposable scalpel blades can be removably attached in such a manner as to reduce the wobble that characterizes known designs.